This invention relates to an improvement in processes for the production of 1,4-dioxan-2-one (p-dioxanone). More particularly, this invention relates to a method for preventing the polymerization of p-dioxanone during processes of its production.
The dehydrogenation of DEG leads to the production of a mixture containing p-dioxanone and unreacted DEG. Pure p-dioxanone is recovered by distilling the mixture under heat and/or reduced pressure. It is well known that DEG initiates the polymerization of p-dioxanone at elevated temperatures. Specifically, the highly reactive hydrogens on DEG's hydroxyl groups function as polymerization initiators.
Several patents, e.g., U.S. Pat. Nos. 5,047,048 and 5,076,807, disclose examples in which DEG is specifically employed as a polymerization initiator. Because DEG tends to initiate polymerization of p-dioxanone at elevated temperatures, the distillation recovery-step results not only in the production of p-dioxanone monomer but in the production of low molecular weight polydioxanone as well. The polymerization of p-dioxanone, in turn, leads to a decrease in the yield of p-dioxanone monomer from the vapor phase dehydrogenation of DEG.
Polymers derived in whole or in part from p-dioxanone have found utility in the fabrication of absorbable medical/surgical devices, e.g., sutures, staples, clips, prostheses, etc. Examples of patents which disclose the polymerization of p-dioxanone alone or in combination with other monomers include, e.g., U.S. Pat. Nos. 4,052,988, 4,643,191, 4,646,741, 4,653,497, 4,788,979, 4,838,267, 5,007,923, 5,047,048, 5,076,807 and 5,080,665. In light of the important end-uses toward which p-dioxanone is employed, improvements in commercially utilized methods of producing p-dioxanone monomer are desired. It would therefore be advantageous to provide processes to prevent the polymerization of p-dioxanone prior to its recovery by distillation as well as to provide processes to facilitate the separation of p-dioxanone from other compounds during the distillation.